System and Method of Measuring Continuous Touch Controller Latency

1. A method of measuring a continuous latency of a touch controller connected to a touch screen display, the method comprising: detecting touch reports from the touch controller and generating a detection signal in response to a change in input direction indicated by the touch reports; capturing a sequence of image frames, each image frame depicting a contact point on the touch screen display and depicting the detection signal outside the touch screen display; and determining a difference between a time t 0 when an actual change in input direction occurred and a time t 1 when the detection signal is generated, based on the image frames, wherein the detection signal is generated by a visual indicator that is not comprised by the touch screen display.

2. The method of claim 1 further comprising determining the time to based on movement of the contact point on the touch screen display in the image frames.

3. The method of claim 2 , wherein the detection signal is a visual signal.

4. The method of claim 1 wherein determining the difference comprises: recording the time to based on visual observation of the contact point on the touch screen display, wherein the touch screen display has a predetermined frame rate; recording the time t 1 based on generation of the detection signal, wherein the detection signal is a visual signal; and counting a number of image frames between the time t 0 and the time t 1 .

5. The method of claim 4 , wherein counting the number of frames comprises: visually recording a movement of the contact point on the touch screen display; identifying a position of the contact point in each of an N-th image frame, an (N−1)-th image frame, and an (N−2)-th image frame, N being a natural number, calculating a first directional vector corresponding to a change in position of the contact point between the N-th image frame and the (N−1)-th image frame, calculating a second directional vector corresponding to a change in position of the contact point between the (N−1)-th image frame and the (N−2)-th image frame, determining that an angle formed by the first and second directional vectors exceeds a predetermined threshold value, and identifying the N-th image frame as the image frame in which the contact changed direction.

6. The method of claim 5 , further comprising identifying an image frame in which the visual signal is generated, comprising: determining a first visual state of the visual indicator in an (N+K−1)-th image frame, K being a natural number, determining a second visual state of the visual indicator in an (N+K)-th image frame, detecting that the first visual state differs from the second visual state, and identifying the (N+K)-th image frame as the image frame in which the visual indicator is updated.

7. The method of claim 6 , wherein the continuous latency is equal to: K F - T ⁢ ⁢ D p , wherein TD p is a constant latency and F is the image capture frame rate.

8. The method of claim 7 , wherein: TD p < 1 F .

9. The method of claim 7 , wherein F is equal to or greater than 1000 frames per second.

10. The method of claim 5 , wherein the predetermined threshold value is 90 degrees.

11. The method of claim 5 , wherein the predetermined threshold value is 45 degrees.

12. The method of claim 4 , wherein identifying a position of the input includes tracking a pattern marker corresponding to an input device.

13. The method of claim 1 , wherein determining the difference between the time t 0 and the time t 1 comprises: identifying a first image frame in which the contact point changed direction; identifying a second image frame in which the detection signal is generated; and calculating the time that elapsed between the first image frame and the second image frame.

14. An apparatus for measuring a continuous latency of a touch controller connected to a touch screen display, the apparatus comprising: a touch detector unit coupled to the touch controller and configured to generate a detection signal in response to a change of input direction of a contact point on the touch screen display, the change of input direction indicated by touch reports output by the touch controller; and a measurement unit configured to capture a sequence of image frames, each image frame depicting a position of a contact point on the touch screen display and depicting the detection signal outside the touch screen display, the measurement unit further determining a difference between a time t 0 when an actual change in input direction occurred and a time t 1 when the detection signal is generated, wherein the detection signal is generated by a visual indicator that is not comprised by the touch screen display.

15. The apparatus of claim 14 , wherein the measurement unit comprises an image recorder that records movement of the contact point on the touch screen display for determination of the time t 0 .

16. The apparatus of claim 14 , wherein the detection signal is a visual signal.

17. The apparatus of claim 16 , wherein the visual indicator comprises a light emitting diode (LED).

18. The apparatus of claim 14 , wherein the measurement unit comprises a computer vision unit configured to calculate the difference on the basis of image frames.

19. A method of measuring a continuous latency of a touch controller connected to a touch screen display, the method comprising: receiving touch reports from the touch controller and generating a detection signal in response to a change of input direction indicated by the touch reports; capturing a sequence of image frames, each image frame including position of a contact point on the touch screen display and depicting the detection signal outside the touch screen display; and counting the number of frames between a first frame depicting change in the position of a contact point and a second frame indicating an updated state of the detection signal, wherein the detection signal is generated by a visual indicator that is not comprised by the touch screen display.

20. The method of claim 19 further comprising determining the first frame by: identifying a position of the contact point in each of an N-th image frame, an (N−1)-th image frame, and an (N−2)-th image frame, N being a natural number, calculating a first directional vector corresponding to a change in position of the contact point between an N-th image frame and an (N−1)-th image frame, calculating a second directional vector corresponding to a change in position of the contact point between the (N−1)-th image frame and an (N−2)-th image frame, determining that an angle formed by the first and second directional vectors exceeds a predetermined threshold value, and identifying the N-th image frame as the image frame in which the contact point changed direction.